Grackles - Are you getting them right?

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Blackbirds in general are often overlooked by birders; or perhaps better said, blackbirds are not often looked at by birders–at least not carefully. Too often we are content to identify these birds as simply ‘Blackbirds’, and move on to more exciting (and colorful) birds. But blackbirds deserve our interest, as well as our scrutiny. As a group they are generally ubiquitous, occurring in large flocks during migration and winter, frequently consisting of multiple species. As such common birds, they are responsible for a large proportion of the important biological interactions that birds have with our ecosystem. Moreover, the blackbirds contain species of conservation concern. Indeed, the Rusty Blackbird has suffered severe population declines over the past few decades, and scientists still struggle to understand its basic biology. Grackles are but one component of this large family, and they are the focus of this piece. Frequently confused by birders, Grackles are not only an identification challenge, but an important part of our avifauna. Understanding range and seasonality can help in the identification process, as the three species’ ranges overlap in relatively few places. Read on to learn more about these birds, and find out if you are indeed ‘getting your Grackles right’!

In North America three grackle species occur: Common, Great-tailed, and Boat-tailed. All are generally similar in appearance, with males glossy iridescent black and females brownish. Great-tailed and Boat-tailed are more closely related, and were once thought to represent the same species. Distinguishing Common Grackle from the others is relatively straight-forward, but separating Great-tailed and Boat-tailed grackles in the field can be more challenging. Luckily, most field guides do a good job of showing the distinctions between these species, yet birders frequently make mistakes with this group. Continuing our series of eBird articles that highlights frequently misidentified common birds, Grackles fit squarely into that niche. While the maps below look good at this scale, zooming in to the state-level often reveals obvious errors. With this article we hope to raise awareness of this ID issue, and we hope you’ll take greater care in reporting future observations of these three species. We touch briefly on the identification of these species below (consult your field guides!), and highlight differences in range and seasonality that should help one arrive at an accurate identification.
Common Grackle

The most widespread of the three, breeding largely east of the Rockies, and wintering throughout the eastern half of the Lower 48. It is the only truly migratory grackle, abandoning the northern portions of its range from Nov-Feb, and augmenting resident breeders across the Southeast. It occurs only as a vagrant in the Pacific states, where it is often confused with the Brewer’s Blackbird. There are two types of Common Grackles that can generally be told apart by plumage. The ‘Bronzed Grackle’ (available in eBird as ‘Common Grackle (Bronzed)’) breeds throughout the northern and western portions of the species’ range, mainly west of the Appalachians. It is migratory, overlapping with the other forms during winter. Best told by its bronzy body plumage, it is generally distinctive, and was once considered a separate species (see below).

The ‘Purple Grackle’ comprises two described subspecies (available in eBird as ‘Common Grackle (Purple)’), and is mostly resident from southern New England east of the Appalachians through Florida. It lacks the bronzy iridescence of the Bronzed Grackle, instead being largely purplish overall (see below), some with a distinctly greenish back. When possible we encourage the reporting of these two forms in eBird.

Common Grackle is smaller than the other two grackle species, with a shorter tail and smaller bill. Males and females are more similar in this species; females generally lack the strong iridescence shown by males, but do not have the buffy brown underparts of Great-tailed/Boat-tailed. Favors open agricultural areas, towns, lawns, but not generally found in marsh. Forms massive flocks in winter, often associating with either or both of the other two species, as well as other blackbirds.
Great-tailed Grackle

This generally southern species is currently expanding its range north and east, and now overlaps with Boat-tailed in Louisiana and east Texas, and with Common more broadly east of the Rockies. It is the largest of the three; males have big bills, flat heads, and very long, keel-shaped tails, often held fanned in flight. It is largely resident throughout its range, but some leave the very northern periphery in winter, withdrawing southward. Despite its recent expansion, it has yet to reach the East Coast, but given its recent trend it could be found anywhere, and should be looked for.

Where Great-tailed overlaps in range with Boat-tailed, the two are best old apart by eye color: Great-tailed has yellow eyes, Boat-tailed has dark eyes (but also see Boat-tailed below). On the bird above, also note the sloping, flat crown, which is generally more rounded in Boat-tailed.
Boat-tailed Grackle

The most range-restricted of the three, Boat-tailed Grackles are very much linked to tidewater, spending their lives near coastal salt marshes; they rarely occur more than a few hundred meters from water across much of their range. The exception to this rule is Florida, where the species occurs inland throughout the peninsula, essentially side-by-side with Common Grackle in many places. Inland records of this species away from Florida should be carefully scrutinized, as it is mainly sedentary, and less prone to wander than the other two.

Male Boat-tailed Grackle, FL, March.

Female Boat-tailed Grackle, FL, March.

Boat-tailed Grackles have variable eye color: along the Atlantic Coast it is yellow, in Florida it is brown, along the eastern Gulf Coast it is yellowish, and along the western Gulf Coast it is brown. The important thing to take home here is that where its range overlaps with Great-tailed, Boat-taileds have brown eyes, and Great-taileds have yellow. But beware of juvenile Great-taileds; their eyes change from amber to yellowish over the course of the first fall and winter.

While this article is meant to draw awareness to this identification challenge, it’s always okay to play-it-safe when you’re not sure and use the more generic reporting forms such as ‘Grackle sp.’ and ‘Great-tailed/Boat-tailed Grackle’. In some cases, mixed flocks of all three species occur numbering in the tens of thousands, and it’s very difficult to sort them out. In these instances it’s fine to be conservative, and use the categories above on your eBird checklists.

We hope this piece inspires you to look more carefully at the grackles in your region, especially if you live in the areas of overlap where two or three species occur together!